Absolutely necessary or requisite; that one cannot do without.
Unbendable, that cannot be set aside or ignored.
A thing that is not dispensable; a necessity.
Very important.
Invigorating or life-giving.
Containing life; living.
Necessary to continued existence.
Necessary to the continuation of life; being the seat of life; being that on which life depends.
Capable of living; in a state to live; viable.
Relating to the recording of life events.
Relating to, or characteristic of life.